1. Field of the Invention
The present invention relates generally to a stream delivery apparatus and method for receiving broadcasts in a mobile broadcast system. More particularly, the present invention relates to a stream delivery apparatus and method for efficiently receiving streams at a mobile terminal in a mobile broadcast system.
2. Description of the Related Art
The mobile communication market continues to create new services through recombination or integration of the existing technologies. With the recent development of the communication and broadcast technologies, the broadcast system or the mobile communication system is now in the phase of providing broadcast service using mobile terminals such as cellular phone and Personal Digital Assistance (PDA). Live discussions are made not only on the common broadcast service limited to the voice and image, but also on Mobile Broadcast Service (BCAST) capable of transmitting packet data over a broadcast channel.
Mobile Broadcast Service can include processes of discovering a service by a mobile terminal capable of receiving Mobile Broadcast Service, subscribing to the service by the mobile terminal, providing various control information for receiving the service, transmitting the service, and receiving the service by the mobile terminal.
FIG. 1 is a diagram illustrating a logical architecture for a mobile broadcast system proposed by BCAST working group of Open Mobile Alliance (OMA) that has established the technical standard for Application Layer and its lower Transport Layer and Network Layer for Mobile Broadcast Service. That is, FIG. 1 illustrates the BCAST network architecture supporting Mobile Broadcast Service. Herein, FIG. 1 illustrates the architecture for OMA BCAST Service, which is an OMA Mobile Broadcast Service standard.
In OMA BCAST, the technical fields and functions being discussed for Mobile Broadcast Service include a service guide having information on Mobile Broadcast Service, necessarily required for discovering Mobile Broadcast Service, service recovery, streaming and file distribution, service and content protection, service provisioning, interaction between a mobile broadcast network and a cellular network, and notification capable of indicating a start of Mobile Broadcast Service and a change in Mobile Broadcast Service. These functions are located in BCAST logical entities shown in FIG. 1. A description will now be made of the logical entities constituting the mobile broadcast system shown in FIG. 1. The logical entities shown in FIG. 1 are shown in Table 1, and interfaces between the entities are shown in Table 2.
TABLE 1No.Entity nameFunctionality102BCAST ServiceRepresents the service application of the BCAST Service, such asApplication (BSA)streaming audio/video or movie file download. It encompasses thefunctionality of media encoding, content protection and interactionrelated to BCAST Service. It also provides the BCAST serviceattributes to the BCAST Service Distribution/Adaptation and BCASTSubscription Management.It may generate charging information, for example, according to theuser charging information that it obtains from the BCASTsubscription management and the content creator. Legacymechanisms may be used for charging information generation anddelivery.103BCAST ServiceResponsible for the aggregation and delivery of BCAST Services, andDistribution/Adaptationperforms the adaptation of the BCAST Enabler to underlying(BSD/A)Broadcast Distribution Systems. It provides the functionality of Fileand Stream Distribution, Service Aggregation, Service Protection,Service Guide generation and delivery, Notification Delivery, and theadaptation to the underlying BDS. The functionality of adaptation toeach BDS may vary depending on the underlying BDS.104BCAST SubscriptionResponsible for service provisioning such as subscription andManagement (BSM)payment related functions, the provision of information used forBCAST Service reception, and BCAST Terminal management.It provides the functionality of Notification, Service Protectionmanagement, Content Protection management, Service Guidegeneration support, Terminal Provisioning and interaction with theBDS Service Distribution to communicate/manage subscriptioninformation with the Terminal.It may send the user charging information to the BCAST serviceapplication.105TerminalThe user device that receives broadcast content as well as the BCASTservice related information, such as, service guide, content protectioninformation. The user device may support the interactive channel inwhich case it would be able to directly communicate to the networkregarding the available services.101Content Creation (CC)Source of content, may provide support for delivery paradigms (e.g.streaming servers); provides base material for content descriptions.111BDS ServiceResponsible for the coordination and delivery of broadcast services toDistributionthe BDS for delivery to the terminal, including file and streamdistribution, and Service Guide distribution. It may also include keydistribution, broadcast subscription management, and accountingfunctions. BDS Service Distribution may not exist in certain BDSs.In that case it would be considered a “Null Function”. It works withthe interactive network to perform service discovery, BDS-specificservice protection and handles other interaction functions. It alsoworks with the BDS for content delivery to the terminal.112Broadcast DistributionSpecific support for the distribution of content over the broadcastSystem (BDS)channel. This may involve the same or different radio network fromthat used by the interactive channel.113Interaction NetworkSpecific support for the interaction channel. This may involve thesame or different radio network from that used by the broadcastchannel.
TABLE 2No.Reference point nameUsage121BCAST-1Content, Content attributes, notification event, etc.122BCAST-2Content-unprotected and/or content-protected BCAST Service,BCAST Service attributes and content attributes.123BCAST-3BCAST Service attributes and content attributes, User preference andsubscription information. User request, User reporting, notificationevent and maybe user charging information124BCASTA-4Notification, Service Guide, fragments (related to provisioning,purchasing, subscription, terminal provisioning, etc.), Service keys,Terminal Provisioning object, Terminal Provisioning message,Terminal management message, etc.125BCAST-5Unprotected and/or protected BCAST Service, content-unprotectedand/or content-protected BCAST Service, BCAST Service attributesand content attributes, Notification, Service Guide, Security material,all distributed over the Broadcast Distribution System.126BCAST-6Unprotected and/or protected BCAST Service, content-unprotectedand/or content-protected BCAST Service, BCAST Service attributesand content attributes, Notification, Service Guide, Security material,terminal reports related to stream and file delivery, all distributed overthe Interaction Network.127BCAST-7Service provisioning, Subscription information, Terminalprovisioning, Security material and device registration.128BCAST-8User interaction, reporting, and user preference129BDS-1Unprotected and/or protected BCAST Service, content-unprotectedand/or content-protected BCAST Service, BCAST Service attributesand content attributes, BDS-specific attributes, Notification andService Guide fragmentsNote: Service protection or Content Protection of RTP streams may beemployed by the BDS itself, if available.130BDS-2Service provisioning, Subscription information, Device management,Security material.131X-1Reference Point between BDS Service Distribution and BDS132X-2Reference Point between BDS Service Distribution and InteractionNetwork133X-3Reference Point between BDS and Terminal134X-4Reference Point between BDS Service Distribution and Terminal overBroadcast135X-5Reference Point between BDS Service Distribution and Terminal overInteraction Channel136X-6Reference Point between Interaction Network and Terminal
In the description of Table 2, ‘reference point’ indicates a connection path between two particular logical entities and can have a plurality of interfaces according to its object. The interfaces are used for communication between two or more functional entities for a particular object, and message types and protocols for the object are used.
FIG. 2 is an exemplary Stream Distribution Function architecture for improving BCAST Streaming Service in OMA BCAST, which is an OMA Mobile Broadcast standard organization.
The Stream Distribution Function converts voice and image data into streams having BCAST standard CODEC or Broadcast Distribution System (BDS) standard CODEC and distributes the converted streams to terminals. The Stream Distribution Function mainly distributes the streams over a broadcast channel, but can also transmit the streams to terminals over an interaction channel when the number of the terminals is smaller.
In addition, the Stream Distribution Function may use service protection capability provided by a Service Protection Function to prevent a terminal or user unauthorized to receive a streaming service from receiving the streaming service, thereby protecting data streams. The Stream Distribution Function may provide an error resilience function in which the terminal can correct a possible stream data error occurring in a wireless environment, using a Forward Error Correction (FEC) technique.
A description of the logical entities and interfaces shown in FIG. 2 is given in Table 3. OMA BCAST configures three sub-functional entities to implement the Stream Distribution Function.
The sub-functional entities include a Stream Application Function, Stream Delivery Function, and Stream Delivery Client Function.
A Content Creation (CC) 101 provides voice or image data to be transmitted as BCAST Streaming Service, and the voice or image data can optionally be a stream that is encoded using BCAST standard media type and CODEC. Further, the CC 101 provides an attribute for the data so that a Stream Application Function (SA) 202 and a Stream Delivery Function (SD) 203 can perform necessary operations, and the attribute may be used for generating a service guide used for an OMA BCAST service guide.
The SA 202 provides a streaming service having BCAST standard media type and CODEC to a plurality of users or user terminals. The SA 202 receives transmission data for the streaming service from the CS 101. The data may have the CODEC and media type defined in OMA BCAST. Otherwise, the data undergoes a translation operation in the SA 202. After completion of the translation operation, the SA 202 delivers the BCAST-standardized stream to the SD 203, along with an attribute for the standardized stream. An exemplary attribute of the standardized stream may include a media type of the stream, a CODEC used, a data-related attribute such as a required rate, a preferred age group for the streaming service, a service area, and the like.
The SD 203 receives the BCAST-standardized stream from the SA 202, and delivers the stream to a plurality of users or user terminals. Accordingly, the SD 203, together with a BDS 112, performs a process of determining a bearer capable of delivering the standardized stream. Further, the SD 203 performs an operation of translating the stream into a streaming service appropriate for the BDS 112, upon receiving a request from the BDS 112. There are two possible methods for delivering streams by the SD 203:                BDS transparent mode: An OMA BCAST-standardized stream is directly delivered in OMA BCAST. In this instance, the BDS 112 provides the bearers and wire/wireless resources to be used for actual transmission, and performs no other function. The SD 203 negotiates bearers to be used for stream delivery in cooperation with a BDS Service Distribution 111 through an SD-B1 interface 217 to deliver the OMA BCAST-standardized stream. If the BDS Service Distribution 111 does not exist, an X-1 interface 131 or an X-2 interface 132 can be used instead of the SD-B1 interface 217. If the bearers are determined, the SD 203 delivers the OMA BCAST-standardized stream to a plurality of terminals via an SD-5 interface 215.        BDS assisted mode: The SD 203 provides the OMA BCAST-standardized stream or stream data to the BDS 112, and the BDS 112 delivers the stream to a plurality of users or user terminals through a translation process appropriate for the BDS characteristics. For the stream delivery, the SD-B1 interface 217 is used. Upon receiving the stream via the SD-B1 interface 217, the BDS Service Distribution 111 distributes the stream to a plurality of users or user terminals after an appropriate translation process.        
In addition, the SD 203 can translate the OMA BCAST stream into a BDS-specific stream in response to a BDS request, and also change a reproduction rate of the stream data according to the network condition of the BDS 112. Further, the SD 203 has a function of protecting a streaming service by using a Service Protection Function to prevent a user or user terminal unauthorized to receive the streaming service from receiving the streaming service, and also a function of delivering signaling information used for reception of the streaming service. In addition, the SD 203 can provide various types of Forward Error Correction (FEC) techniques capable of reducing a delivery error rate of the streaming service taking the wireless channel environment into account.
A Stream Delivery Client Function (SD-C) 204 receives streams on a broadcast channel or an interaction channel via an SD-5 interface 215, or an interface provided in the BDS 112, has a function of decoding the service-protected streams and an error resilience function for FEC-applied streams, and can also have a function (for example, media synchronization function) necessary for reception of the streaming service. In addition, the SD-C 204 can have a function capable of reporting a reception error rate for the received streaming service according to capability of the mobile terminal. Herein, the term “capability of the terminal” refers to the capability of communicating with the SD 203 or the BDS 112 using a cellular network or other networks.
TABLE 3No.InterfaceReference pointDescription211SD-1BCAST-1Delivery of an unprocessed stream for BCAST streaming ServiceDelivery of stream with media type and CODEC supported byBCAST212SD-2BCAST-2Delivery of a stream having BCAST standard media type andCODECDelivery of stream attributes to Stream Distribution Function inBCAST Service Distribution/Adaptation215SD-5BCAST-5Unidirectional delivery of a BCAST-standardized stream.Unidirectional delivery of a stream, which is adapted to BDSspecific condition(.e.g a data rate supported by BDS)Unidirectional delivery of in-band signaling for StreamDistribution(e.g. signaling used for stream reception)216SD-6BCAST-6Delivery of report about a stream receptionDelivery of request from terminal e.g. request for the retransmissionof a whole stream217SD-B1BCAST-1Delivery of a stream to BDSDelivery of a protected stream to BDSDelivery of a stream attribute to determine bearers used for streamdistributionDelivery of bearer information used for a stream distributionDelivery of a BDS specific profiles for the adaptation of Stream toBDSNote:If BDS service distribution does not exist, then x-1 and/or x-2 can be used for the same purpose
As described with reference to FIG. 2, the functional entities for stream distribution are defined. However, definitions of (i) how to actually perform stream distribution, (ii) which control messages should be delivered between the functional entities for actual stream distribution, and (iii) how the functions to be provided in the Stream Distribution Function should be implemented.